Display panel with touch detection function, method of driving the same, driving circuit, and electronic unit

ABSTRACT

A display panel with a touch detection function, in which display operation is less affected by touch detection operation, a method of driving the display panel with a touch detection function, a driving circuit, and an electronic unit having the display panel with a touch detection function are disclosed. The display panel with a touch detection function includes: one or more display elements; one or more drive electrodes; one or more touch detection electrodes; and a drive section selectively applying a DC drive signal or an AC drive signal to the drive electrodes.

CROSS REFERENCES TO RELATED APPLICATIONS

This is a Continuation Application of the U.S. Pat. Application No.:17/673,872, filed Feb. 17, 2022, which is a Continuation Application ofthe U.S. Pat. Application No.: 17/204,182, filed Mar. 17, 2021, now Pat.No.: 11,287,916, issued on Mar. 29, 2022, which is a ContinuationApplication of the U.S. Pat. Application No.: 16/738,584, filed Jan. 9,2020, now Pat. No.: 10,983,623, issued on Apr. 20, 2021, which is aContinuation Application of the U.S. Pat. Application No.: 16/236,765,filed Dec. 31, 2018, now Pat. No.: 10,572,090, issued on Feb. 25, 2020,which is a Continuation Application of the U.S. Pat. Application No.:15/959,742, filed Apr. 23, 2018, now Pat. No.: 10,203,829, issued onFeb. 12, 2019, which is a Continuation Application of the U.S. Pat.Application No.: 15/845,740, filed Dec. 18, 2017, now Pat. No.:10,013,131, issued on Jul. 3, 2018, which is a Continuation Applicationof the U.S. Pat. Application No.: 15/630,091, filed Jun. 22, 2017, nowPat. No.: 9,864,473, issued on Jan. 9, 2018, which is a ContinuationApplication of the U.S. Pat. Application No.: 14/842,291, filed Sep. 1,2015, now Pat. No.: 9,715,318, issued on Jul. 25, 2017, which is aContinuation Application of the U.S. Pat. Application No. 14/306,633,filed Jun. 17, 2014, now Patent No.: 9,141,247, issued on Sep. 22, 2015,which is a Continuation Application of the U.S. Pat. Application No.:13/414,363, filed Mar. 7, 2012, now Patent No.: 8,791,916, issued onJul. 29, 2014, which claims priority from Japanese Patent ApplicationNo.: 2011-089429, filed Apr. 13, 2011, and Japanese Patent ApplicationNo.: 2011-242797, filed Nov. 4, 2011, the entire contents of which beingincorporated herein by reference.

BACKGROUND

The present disclosure relates to a display panel with a touch detectionfunction of detecting a touch event due to an external proximity object,a method of driving the same, a driving circuit, and an electronic unithaving the display panel with a touch detection function.

Recently, a display panel has been notified, where a touch detectiondevice, a so-called touch panel, is mounted on a display unit such as aliquid crystal display unit, or the touch panel is integrated with thedisplay unit, and various button images and the like are displayed onthe display unit for inputting information, instead of typicalmechanical buttons. Such a display panel having the touch panel needsnot have an input device such as a keyboard, a mouse, and a keypad andtherefore tends to be expansively used not only for computers but alsofor handheld information terminals such as mobile phones.

A type of the touch panel includes several types such as an optical typeand a resistant type. In particular, a capacitance-type touch panel hasbeen promising as a device allowing low power consumption with arelatively simple structure. For example, Japanese Unexamined PatentApplication Publication No. 2009-244958 (JP-A-2009-244958) proposes aso-called in-cell-type display panel with a touch detection function,where a common-electrode originally provided for display of a displayunit is used also as one of a pair of electrodes for a touch sensor, andthe other electrode (touch detection electrode) is disposed to intersectthe common electrode. In addition, several propositions have been madeon a so-called on-cell-type display panel with a touch detectionfunction, in which a touch panel is provided on a display surface of adisplay unit.

SUMMARY

In the display panel with a touch detection function, since a displayfunction is integrated with the touch detection function, for example,display operation may be affected by operation for touch detection.However, JP-A-2009-244958 has no description on such influence andmeasures against the influence.

It is desirable to provide a display panel with a touch detectionfunction, in which display operation is less affected by touch detectionoperation, a method of driving the display panel with a touch detectionfunction, a driving circuit, and an electronic unit having the displaypanel with a touch detection function.

A display panel with a touch detection function according to anembodiment of the disclosure includes one or more display elements; oneor more drive electrodes; one or more touch detection electrodes; and adrive section. The drive section selectively applies a DC drive signalor an AC drive signal to the drive electrodes.

A method of driving the display panel with a touch detection functionaccording to an embodiment of the disclosure includes driving one ormore display elements for display, and selectively applying a DC drivesignal or an AC drive signal to the one or more drive electrodes.

A drive circuit according to an embodiment of the disclosure includes adisplay drive section and a touch detection drive section. The displaydrive section drives one or more display elements. The touch detectiondrive section selectively applies a DC drive signal or an AC drivesignal to one or more drive electrodes.

An electronic unit according to an embodiment of the disclosure includesa display panel with a touch detection function, and a control sectioncontrolling operation using the display panel with a touch detectionfunction. The display panel with a touch detection function includes oneor more display elements, one or more drive electrodes, one or moretouch detection electrodes, and a drive section selectively applying aDC drive signal or an AC drive signal to the drive electrodes. Such anelectronic unit includes, for example, a television apparatus, a digitalcamera, a personal computer, a video camera, and a mobile terminaldevice such as a mobile phone.

In the display panel with a touch detection function and the method ofdriving the display panel with a touch detection function, the drivecircuit, and the electronic unit according to the embodiments of thedisclosure, the display elements are driven for display, a drive signalis applied to the drive electrodes, and the touch detection electrodesoutput a signal corresponding to the drive signal. At that time, one ofthe DC drive signal and the AC drive signal is selectively applied asthe drive signal to the drive electrodes.

According to the display panel with a touch detection function and themethod of driving the display panel with a touch detection function, thedrive circuit, and the electronic unit according to the embodiments ofthe disclosure, since the DC drive signal or the AC drive signal isselectively applied to the drive electrodes, display operation is lessaffected by touch detection operation.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the technology as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments and,together with the specification, serve to explain the principles of thetechnology.

FIG. 1 is a diagram for explaining a basic principle of a touchdetection process of a display panel with a touch detection functionaccording to embodiments of the disclosure, showing a state where afinger is not in contact with or not in proximity to the display panel.

FIG. 2 is a diagram for explaining the basic principle of the touchdetection process of the display panel with a touch detection functionaccording to the embodiments of the disclosure, showing a state where afinger is in contact with or in proximity to the display panel.

FIG. 3 is a diagram for explaining the basic principle of the touchdetection process of the display panel with a touch detection functionaccording to the embodiments of the disclosure, showing exemplarywavefordrawingsms of a drive signal and a touch detection signal.

FIG. 4 is a block diagram illustrating an exemplary configuration of adisplay panel with a touch detection function according to a firstembodiment of the disclosure.

FIG. 5 is a block diagram illustrating an exemplary configuration of aselectionswitch section shown in FIG. 4 .

FIG. 6 is a sectional diagram illustrating a schematic sectionalstructure of a display device with a touch detection function shown inFIG. 4 .

FIG. 7 is a circuit diagram illustrating a pixel arrangement in thedisplay device with a touch detection function shown in FIG. 4 .

FIG. 8 is a perspective diagram illustrating exemplary configurations ofdrive electrodes and touch detection electrodes of the display devicewith a touch detection function shown in FIG. 4 .

FIGS. 9A to 9C are schematic diagrams illustrating an exemplaryoperation of touch detection scan of the display panel with a touchdetection function shown in FIG. 4 .

FIG. 10 is a schematic diagram illustrating exemplary operations ofdisplay scan and touch detection scan of the display panel with a touchdetection function shown in FIG. 4 .

FIG. 11 is a block diagram illustrating an exemplary configuration of adrive signal generation section shown in FIG. 4 .

FIG. 12 is a block diagram illustrating an exemplary configuration of adrive electrode driver according to the first embodiment.

FIG. 13 is a timing waveform chart illustrating an exemplary operationof the display panel with a touch detection function according to thefirst embodiment.

FIG. 14 is a timing waveform chart illustrating an exemplary touchdetection operation of the display panel with a touch detection functionaccording to the first embodiment.

FIG. 15 is a block diagram illustrating an exemplary configuration of adrive signal generation section according to a comparative example.

FIG. 16 is a block diagram illustrating an exemplary configuration of adrive electrode driver according to the comparative example.

FIG. 17 is a timing waveform chart illustrating an exemplary operationof a display panel with a touch detection function according to thecomparative example.

FIG. 18 is a block diagram illustrating an exemplary configuration of adrive signal generation section according to a modification of theembodiment.

FIG. 19 is a block diagram illustrating an exemplary configuration of adrive electrode driver according to another modification of theembodiment.

FIGS. 20A to 20C are schematic diagrams illustrating an exemplaryoperation of touch detection scan according to a still anothermodification of the embodiment.

FIG. 21 is a timing waveform chart illustrating an exemplary operationof a display panel with a touch detection function according to a stillanother modification of the embodiment.

FIG. 22 is a block diagram illustrating an exemplary configuration of adrive electrode driver according to a second embodiment.

FIG. 23 is a timing waveform chart illustrating an exemplary operationof the display panel with a touch detection function according to thesecond embodiment.

FIG. 24 is a timing waveform chart illustrating an exemplary touchdetection operation of the display panel with a touch detection functionaccording to the second embodiment.

FIG. 25 is a perspective diagram illustrating an appearanceconfiguration of an application example 1, among display panels with atouch detection function applied with the embodiments.

FIGS. 26A and 26B are perspective diagrams illustrating an appearanceconfiguration of an application example 2.

FIG. 27 is a perspective diagram illustrating an appearanceconfiguration of an application example 3.

FIG. 28 is a perspective diagram illustrating an appearanceconfiguration of an application example 4.

FIGS. 29A to 29G are front diagrams, side diagrams, a top diagram, and abottom diagram illustrating an appearance configuration of anapplication example 5.

FIG. 30 is a sectional diagram illustrating a schematic sectionalstructure of a display device with a touch detection function accordingto a modification.

DETAILED DESCRIPTION

Hereinafter, embodiments of the disclosure will be described in detailwith reference to the accompanying drawings. It is to be noted thatdescription is made in the following order.

-   1. Basic Principle of Capacitance-Type Touch Detection-   2. First Embodiment-   3. Second Embodiment-   4. Application Examples

1. Basic Principle of Capacitance-Type Touch Detection

First, a basic principle of touch detection of a display panel with atouch detection function according to embodiments of the disclosure isdescribed with reference to FIGS. 1 to 3 . This touch detection processis embodied as a capacitance-type touch sensor. In the capacitance-typetouch sensor, for example, a pair of electrodes (drive electrode E1 andtouch detection electrode E2) disposed to face each other with adielectric body D in between are used to configure a capacitanceelement, as illustrated in (A) of FIG. 1 . Such a structure is expressedas an equivalent circuit illustrated in (B) of FIG. 1 . The driveelectrode E1, the touch detection electrode E2, and the dielectric bodyD define a capacitance element C1. One end of the capacitance element C1is connected to an AC signal source (drive signal source) S, and theother end P is grounded through a resistor R and connected to a voltagedetector (a touch detection circuit) DET. After an AC rectangular waveSg ((B) of FIG. 3 ) having a predetermined frequency (for example,approximately several kilohertz to several tens kilohertz) is appliedfrom the AC signal source S to the drive electrode E1 (a first end ofthe capacitance element C1), an output waveform (a touch detectionsignal) Vdet, as illustrated in (A) of FIG. 3 is shown at the touchdetection electrode E2 (a second end P of the capacitance element C1).It is to be noted that the AC rectangular wave Sg corresponds to an ACdrive signal VcomAC described below.

In a state where a finger is not in contact with (or not in proximityto) the display panel, current I0 corresponding to a capacitance valueof the capacitance element C1 flows in response to charge and dischargewith respect to the capacitance element C1 as illustrated in FIG. 1 .Here, a potential waveform at the second end P of the capacitanceelement C1 is, for example, as shown by a waveform V0 in (A) of FIG. 3 ,which is detected by the voltage detector DET.

On the other hand, in a state where a finger is in contact with (or inproximity to) the display panel, a capacitance element C2 is formed by afinger and is added in series to the capacitance element C1 asillustrated in FIG. 2 . In this state, a current I1 and a current I2flow in response to charge and discharge of the capacitance elements C1and C2, respectively. Here, a potential waveform at the second end P ofthe capacitance element C1 is, for example, as shown by a waveform V1 in(A) of FIG. 3 , which is detected by the voltage detector DET. Here,electric potential of the point P corresponds to a divided potentialdetermined by the values of the currents I1 and I2 flowing through therespective capacitance elements C1 and C2. The waveform V1, therefore,has a small value compared with the waveform V0 in the non-contactstate. The voltage detector DET compares a detected voltage with apredetermined threshold voltage Vth. If the detected voltage is equal toor higher than the threshold voltage, the voltage detector DETdetermines that no contact occurs. If the detected voltage is lower thanthe threshold voltage, the voltage detector DET determines that somecontact occurs. In this way, touch detection is performed.

2. First Embodiment Exemplary Configuration Exemplary OverallConfiguration

FIG. 4 illustrates an exemplary configuration of a display panel with atouch detection function 1 according to a first embodiment. The displaypanel includes liquid crystal display elements as display elements, andis a so-called in-cell type display panel, in which a liquid crystaldisplay device configured of the liquid crystal display elements isintegrated with a capacitance-type touch detection device.

The display panel with a touch detection function 1 includes a controlsection 11, a gate driver 12, a source driver 13, a selection switchsection 14, a drive signal generation section 15, a drive electrodedriver 16, a display device with a touch detection function 10, and atouch detection section 40.

The control section 11 is a circuit that supplies a control signal toeach of the gate driver 12, the source driver 13, the drive signalgeneration section 15, the drive electrode driver 16, and the touchdetection section 40 based on a video signal Vdisp supplied from theoutside, and controls the components to operate in synchronization withone another.

The gate driver 12 has a function of sequentially selecting onehorizontal line as a display drive object in the display device with atouch detection function 10 based on the control signal supplied fromthe control section 11. In detail, the gate driver 12 generates a scansignal Vscan based on the control signal supplied from the controlsection 11, and applies the scan signal Vscan to a gate of a TFT elementTr of each pixel Pix through a scan signal line GCL to sequentiallyselect one row (one horizontal line) as a display drive object of pixelsPix provided in a matrix in a liquid crystal display device 20 of thedisplay device with a touch detection function 10.

The source driver 13 generates and outputs a pixel signal Vsig based ona video signal and a source driver control signal supplied from thecontrol section 11. In detail, the source driver 13 generates the pixelsignal Vsig, in which pixel signals Vpix for a plurality of (here,three) sub-pixels SPix of the liquid crystal display device 20 of thedisplay device with a touch detection function 10 are time-divisionallymultiplexed, from a video signal corresponding to one horizontal line,and supplies the pixel signal Vsig to the selection switch section 14,as described below. In addition, the source driver 13 generates aswitching control signal Vsel (VselR, VselG, and VselB) necessary fordemultiplexing the pixel signals Vpix multiplexed into the pixel signalVsig, and supplies the switching control signal Vsel together with thepixel signal Vsig to the selection switch section 14. It is to be notedthat such multiplexing is performed to reduce the number of wiringsbetween the source driver 13 and the selection switch section 14.

The selection switch section 14 demultiplexes the pixel signals Vpix,which have been time-divisionally multiplexed into the pixel signalVsig, based on the pixel signal Vsig and the switching control signalVsel supplied from the source driver 13, and supplies the pixel signalsVpix to the liquid crystal display device 20 of the display device witha touch detection function 10.

FIG. 5 illustrates an exemplary configuration of the selection switchsection 14. The selection switch section 14 has a plurality of switchgroups 17. Each switch group 17 includes three switches SWR, SWG, andSWB herein, where respective first ends of the switches are connected toone another and supplied with a pixel signal Vsig from the source driver13, and respective second ends thereof are connected to three sub-pixelsSPix (R, G, and B) relevant to a pixel Pix through pixel signal linesSGL of the liquid crystal display device 20 of the display device with atouch detection function 10. The respective three switches SWR, SWG, andSWB are controlled to be on or off by the switching control signal Vsel(VselR, VselG, and VselB) supplied from the source driver 13. Accordingto such a configuration, the selection switch section 14 sequentiallychanges the three switches SWR, SWG, and SWB in a time-divisional mannerto be on in response to the switching control signal Vsel, therebydemultiplexing the pixel signals Vpix (VpixR, VpixG, and VpixB) from themultiplexed pixel signal Vsig. In addition, the selection switch section14 supplies the respective pixel signals Vpix to the three sub-pixelsSPix (R, G, and B).

The drive signal generation section 15 generates a drive signal Vcombased on a control signal supplied from the control section 11. Indetail, the drive signal generation section 15 generates a DC drivesignal VcomDC and generates an AC drive signal VcomAC based on a Vcomcontrol signal EXVCOM (described below) supplied from the controlsection 11, and supplies the signals to the drive electrode driver 16,as described below. The DC drive signal VcomDC is a DC signal having avoltage of 0 V. The AC drive signal VcomAC has a pulse waveform having alow-level voltage of 0 V and a high-level voltage of VH.

The drive electrode driver 16 is a circuit that supplies the drivesignal Vcom to drive electrodes COML (described below) of the displaydevice with a touch detection function 10 based on a control signalsupplied from the control section 11. In detail, the drive electrodedriver 16 applies the AC drive signal VcomAC to the relevant driveelectrodes COML in touch detection operation. At that time, the driveelectrode driver 16 drives the drive electrodes COML by one block (driveelectrode block B described below) including a predetermined number ofdrive electrodes COML at a time. In addition, the drive electrode driver16 applies the DC drive signal VcomDC to the drive electrodes COML otherthan the drive electrodes COML relevant to the touch detectionoperation.

The display device with a touch detection function 10 is a displaydevice in which a touch detection function is embedded. The displaydevice with a touch detection function 10 includes the liquid crystaldisplay device 20 and a touch detection device 30. The liquid crystaldisplay device 20 performs sequential scan by one horizontal line basisfor performing display in response to scan signals Vscan supplied fromthe gate driver 12, as described below. The touch detection device 30operates on the basis of the above-described basic principle of thecapacitance-type touch detection and outputs a touch detection signalVdet. The touch detection device 30 performs sequential scan in responseto the AC drive signal VcomAC supplied from the drive electrode driver16 to perform touch detection, as described below.

The touch detection section 40 detects presence of a touch event in thetouch detection device 30 based on a touch detection control signalsupplied from the control section 11 and the touch detection signal Vdetsupplied from the touch detection device 30 of the display device with atouch detection function 10, and obtains the coordinates of a touchevent in a touch detection region if the touch event is detected. Thetouch detection section 40 includes a low pass filter (LPF) section 42,an A/D conversion section 43, a signal processing section 44, acoordinate extraction section 45, and a detection timing control section46. The LPF section 42 is a low-pass analog filter that removes thehigh-frequency components (noise components) contained in the touchdetection signal Vdet supplied from the touch detection device 30, andthus extracts and outputs the touch components. A resistance R forproviding a DC potential (0 V) is connected between each of inputterminals of the LPF section 42 and ground. It is to be noted that, forexample, a switch may be provided in place of the resistance R such thatthe switch is turned on at a predetermined timing so as to provide theDC potential (0 V). The A/D conversion section 43 is a circuit thatsamples each of the analog signals output from the LPF section 42 at atiming in synchronization with the AC drive signal VcomAC, and convertsthe analog signals to digital signals. The signal processing section 44is a logical circuit that detects presence of a touch event in the touchdetection device 30 based on signals output from the A/D conversionsection 43. The coordinate extraction section 45 is a logical circuitthat determines touch-panel coordinates of a touch event if signalprocessing section 44 detects a touch event. The detection timingcontrol section 46 controls these circuits to operate in synchronizationwith one another.

Display Device With Touch Detection Function 10

An exemplary configuration of the display device with a touch detectionfunction 10 is now described in detail.

FIG. 6 illustrates an exemplary sectional structure of a major part ofthe display device with a touch detection function 10. The displaydevice with a touch detection function 10 includes a pixel substrate 2,a counter substrate 3 disposed to face the pixel substrate 2, and aliquid crystal layer 6 interposed between the pixel substrate 2 and thecounter substrate 3.

The pixel substrate 2 includes a TFT substrate 21 as a circuitsubstrate, the drive electrodes COML, and pixel electrodes 22. The TFTsubstrate 21 functions as a circuit substrate on which various kinds ofelectrodes, wirings, thin film transistors (TFTs), and the like areprovided. The TFT substrate 21 is configured of, for example, glass. Thedrive electrodes COML are provided on the TFT substrate 21. The driveelectrodes COML are electrodes for supplying the common voltage to aplurality of pixels Pix (described below). The drive electrodes COMLfunction as a common drive electrode for liquid crystal displayoperation, and also function as the drive electrodes for touch detectionoperation. An insulating layer 23 is provided on the drive electrodesCOML, and the pixel electrodes 22 are provided on the insulating layer23. The pixel electrodes 22 are translucent electrodes for supplying thepixel signals for performing display. The drive electrodes COML and thepixel electrodes 22 include, for example, indium tin oxide (ITO).

The counter substrate 3 includes a glass substrate 31, a color filter32, and touch detection electrodes TDL. The color filter 32 is providedon a first surface of the glass substrate 31. The color filter 32 isconfigured of, for example, color filter layers of three colors of red(R), green (G), and blue (B) arranged periodically, where a set of threecolors R, G, and B is associated with each display pixel. The touchdetection electrodes TDL are provided on a second surface of the glasssubstrate 31. The touch detection electrodes TDL, which are translucent,include for example, ITO. A polarizing plate 35 is disposed on the touchdetection electrodes TDL

The liquid crystal layer 6 acts as a display function layer thatmodulates light passing through the liquid crystal layer 6 depending ona state of an electric field. The electric field is formed by adifference in electric potential between the voltage of the driveelectrode COML and the voltage of the pixel electrode 22. Atransverse-mode liquid crystal, such as fringe field switching (FFS)liquid crystal and in-plane switching (IPS) liquid crystal, is used forthe liquid crystal layer 6.

It is to be noted that an alignment film is provided between the liquidcrystal layer 6 and the pixel substrate 2 and between the liquid crystallayer 6 and the counter substrate 3, and an incidence-side polarizingplate is disposed on a bottom of the pixel substrate 2, which areomitted to be shown herein.

FIG. 7 illustrates an exemplary configuration of a pixel structure ofthe liquid crystal display device 20. The liquid crystal display device20 has a plurality of pixels Pix arranged in a matrix. Each pixel Pix isconfigured of three sub-pixels SPix. The respective, three sub-pixelsSPix are disposed in correspondence to the three colors (RGB) of thecolor filter 32 shown in FIG. 6 . Each sub-pixel SPix includes a TFTelement Tr and a liquid crystal element LC. The TFT element Tr isconfigured of a thin film transistor which is an n-channel metal oxidesemiconductor (MOS) TFT herein. A source of the TFT element Tr isconnected to the pixel signal line SGL, a gate thereof is connected tothe scan signal line GCL, and a drain thereof is connected to a firstend of the liquid crystal element LC. A first end of the liquid crystalelement LC is connected to the drain of the TFT element Tr, and thesecond end thereof is connected to the drive electrode COML.

The sub-pixel SPix is connected mutually with other sub-pixels SPix onthe same row of the liquid crystal display device 20 through the scansignal line GCL. The scan signal line GCL is connected to the gatedriver 12 and is supplied with the scan signal Vscan from the gatedriver 12. In addition, the sub-pixel SPix is connected mutually withother sub-pixels SPix on the same column of the liquid crystal displaydevice 20 through the pixel signal line SGL. The pixel signal line SGLis connected to the selection switch section 14 and is supplied with thepixel signal Vpix from the selection switch section 14.

Furthermore, the sub-pixel SPix is connected mutually with othersub-pixels SPix on the same row of the liquid crystal display device 20through the drive electrode COML. The drive electrode COML is connectedto the drive electrode driver 16 and is supplied with the drive signalVcom (DC drive signal VcomDC) from the drive electrode driver 16.

According to such a configuration, in the liquid crystal display device20, the gate driver 12 drives the scan signal lines GCL to beline-sequentially scanned in a time-divisional manner, thereby onehorizontal line is sequentially selected, and the source driver 13 andthe selection switch section 14 supply the pixel signals Vpix to pixelsPix along the one horizontal line, so that display is performed by onehorizontal line basis.

FIG. 8 perspectively illustrates an exemplary configuration of the touchdetection device 30. The touch detection device 30 is configured of thedrive electrodes COML provided on the pixel substrate 2 and the touchdetection electrodes TDL provided on the counter substrate 3. The driveelectrodes COML are configured as a plurality of stripe-shaped electrodepatterns extending in a horizontal direction in the figure. In the touchdetection operation, the AC drive signal VcomAC is sequentially suppliedto each of the electrode patterns by the drive electrode driver 16 sothat the electrode patterns are driven to be sequentially scanned in atime-divisional manner as described below. The touch detectionelectrodes TDL are configured of stripe-shaped electrode patternsextending in a direction orthogonal to the extending direction of theelectrode patterns of the drive electrodes COML. The electrode patternof each of the touch detection electrode TDL is connected to input partsof the LPF section 42 of the touch detection section 40. The electrodepatterns of the drive electrode COML intersect the electrode patterns ofthe touch detection electrode TDL, resulting in formation of capacitanceat respective intersections.

According to such a configuration, in the touch detection device 30, thedrive electrode driver 16 applies the AC drive signal VcomAC to thedrive electrodes COML, so that the touch detection electrodes TDL outputthe touch detection signal Vdet for touch detection. Specifically, thedrive electrodes COML correspond to the drive electrode E1 in the basicprinciple of touch detection illustrated in FIGS. 1 to 3 , and the touchdetection electrodes TDL correspond to the touch detection electrode E2.The touch detection device 30 detects a touch event in accordance withthe basic principle. As illustrated in FIG. 8 , a capacitance-type touchsensor is formed in a matrix by the electrode patterns intersecting eachother. Accordingly, a position of contact or proximity of an externalproximity object is detected by scanning the entire touch detectionsurface of the touch detection device 30.

FIGS. 9A to 9C schematically illustrate touch detection scan. FIGS. 9Ato 9C show application operation of the AC drive signal VcomAC to eachof twenty drive electrode blocks B 1 to B20 which define a displayscreen/touch detection surface herein. A drive-signal-applied block BACindicates a drive electrode block B to which the AC drive signal VcomACis applied, while the DC drive signal VcomDC is applied to other driveelectrode blocks B. The drive electrode driver 16 sequentially selects adrive electrode block B as an object of touch detection operation andapplies the AC drive signal VcomAC to the selected drive electrode blockB so as to scan all the drive electrode blocks B, as shown in FIGS. 9Ato 9C. During such operation, the drive electrode driver 16 applies theAC drive signal VcomAC to each drive electrode block B over a pluralityof predetermined horizontal periods as described below. While the numberof the drive electrode blocks B is twenty for convenience of descriptionherein, this is not limitative.

FIG. 10 schematically illustrates display scan and touch detection scan.In the display panel with a touch detection function 1, the gate driver12 drives the scan signal lines GCL to be line-sequentially scanned in atime-divisional manner so as to perform display scan Scand, and thedrive electrode driver 16 sequentially selects the drive electrode blockB to be driven so as to perform touch detection scan Scant. Here, thetouch detection scan Scant is performed at a scan speed two times ashigh as the display scan Scand. In this way, in the display panel with atouch detection function 1, the scan speed of touch detection is higherthan that of display scan, allowing a prompt response to a touch eventdue to an external proximity object, and leading to an improvement inresponse characteristics for touch detection. It is to be noted that theabove scan is not limitative, and, for example, the touch detection scanScant may be performed at a scan speed two times or more as high as thedisplay scan Scand, or may be performed at a scan speed two times orless as high as the display scan Scand.

Drive Signal Generation Section 15 and Drive Electrode Driver 16

FIG. 11 illustrates an exemplary configuration of the drive signalgeneration section 15. The drive signal generation section 15 includes ahigh-level-voltage generation sub-section 61, a low-level-voltagegeneration sub-section 62, buffers 63 to 65, and a switching circuit 66.

The high-level-voltage generation sub-section 61 generates a high-levelvoltage of the AC drive signal VcomAC. The low-level-voltage generationsub-section 62 generates a DC voltage of the DC drive signal VcomDC. Thevoltage generated by the low-level-voltage generation sub-section 62 isalso used as a low-level voltage of the AC drive signal VcomAC. Thebuffer 63 outputs the voltage supplied from the high-level-voltagegeneration sub-section 61 to the switching circuit 66 while performingimpedance conversion of the voltage. The buffer 64 outputs the voltagesupplied from the low-level-voltage generation sub-section 62 to theswitching circuit 66 while performing impedance conversion of thevoltage. The switching circuit 66 generates the AC drive signal VcomACbased on the Vcom control signal EXVCOM. In detail, if the Vcom controlsignal EXVCOM is high, the switching circuit 66 outputs the voltagesupplied from the buffer 63, and if the Vcom control signal EXVCOM islow, it outputs the voltage supplied from the buffer 64. The buffer 65outputs the voltage supplied from the low-level-voltage generationsub-section 62 as the DC drive signal VcomDC while performing impedanceconversion of the voltage. The buffers 63 to 65 are each configured of avoltage follower, for example.

FIG. 12 illustrates an exemplary configuration of the drive electrodedriver 16. The drive electrode driver 16 includes a scan control section51, a touch detection scan section 52, and a drive section 530. Thedrive section 530 includes twenty drive sub-sections 53(1) to 53(20).Hereinafter, any one of the twenty drive sub-sections 53(1) to 53(20) issimply referred to as drive sub-section 53.

The scan control section 51 supplies a control signal to the touchdetection scan section 52 based on a control signal supplied from thecontrol section 11. In addition, the scan control section 51 has afunction of supplying a Vcom selection signal VCOMSEL to the drivesection 530. The Vcom selection signal VCOMSEL indicates appropriate oneof the DC drive signal VcomDC and the AC drive signal VcomAC to besupplied to the drive electrodes COML,.

The touch detection scan section 52 includes a shift register, andgenerates scan signals St for selecting the drive electrodes COML towhich the AC drive signal VcomAC is applied. In detail, the touchdetection scan section 52 generates a plurality of scan signals Stcorresponding to the drive electrode blocks B based on the controlsignal supplied from the scan control section 51, as described below. Inthe case where the touch detection scan section 52 supplies a high-levelsignal to a kth drive sub-section 53(k) as a kth scan signal St(k), forexample, the drive sub-section 53(k) applies the AC drive signal VcomACto a plurality of drive electrodes COML in a kth drive electrode blockB(k).

The drive section 530 applies the DC drive signal VcomDC or the AC drivesignal VcomAC supplied from the drive signal generation section 15 tothe drive electrodes COML based on the scan signal St supplied from thetouch detection scan section 52 and the Vcom selection signal VCOMSELsupplied from the scan control section 51. The drive sub-section 53 isprovided by one in correspondence to each of the signals output from thetouch detection scan section 52 so as to apply the drive signal Vcom toa corresponding drive electrode block B.

The drive sub-section 53 includes an AND gate 54, an inverter 55,buffers 56 and 57, and switches SW1 and SW2. The AND gate 54 generates alogical product (AND) of the scan signal St supplied from the touchdetection scan section 52 and the Vcom selection signal VCOMSEL suppliedfrom the scan control section 51, and outputs the logical product. Theinverter 55 generates an inverting logic of the signal output from theAND gate 54 and outputs the inverting logic. The buffer 56 has afunction of amplifying the signal supplied from the AND gate 54 to anamplitude level allowing on/off control of the switch SW1. The switchSW1 is controlled to be on or off based on the signal supplied from thebuffer 56, and has a first end to which the AC drive signal VcomAC issupplied, and a second end connected to the plurality of driveelectrodes COML defining the drive electrode block B. The buffer 57 hasa function of amplifying the signal supplied from the inverter 55 to anamplitude level allowing on/off control of the switch SW2. The switchSW2 is controlled to be on or off based on the signal supplied from thebuffer 57, and has a first end to which the DC drive signal VcomDC issupplied, and a second end connected to the second end of the switchSW1.

According to such a configuration, if the scan signal St is high, thedrive sub-section 53 outputs the AC drive signal VcomAC as the drivesignal Vcom while the Vcom selection signal VCOMSEL is high, and outputsthe DC drive signal VcomDC as the drive signal Vcom while the Vcomselection signal VCOMSEL is low. If the scan signal St is low, the drivesub-section 53 outputs the DC drive signal VcomDC as the drive signalVcom. The drive signal Vcom output from the drive sub-section 53 in thisway is supplied to a plurality of drive electrodes COML defining thedrive electrode block B corresponding to the drive sub-section 53.

The liquid crystal element LC corresponds to a specific example of“display element” of the disclosure. The drive electrode driver 16corresponds to a specific example of “drive section” of the disclosure.The high-level-voltage generation sub-section 61 and the buffer 63correspond to a specific example of “first voltage generationsub-section” of the disclosure. The low-level-voltage generationsub-section 62 corresponds to a specific example of “second voltagegeneration sub-section” of the disclosure. The buffer 64 corresponds toa specific example of “buffer circuit” of the disclosure.

Operations and Functions

Operations and functions of the display panel with a touch detectionfunction 1 according to the embodiment are now described.

Summary of General Operation

Summary of general operation of the display panel with a touch detectionfunction 1 is described with reference to FIG. 4 . The control section11 supplies the control signal to each of the gate driver 12, the sourcedriver 13, the drive signal generation section 15, the drive electrodedriver 16, and the touch detection section 40 based on a video signalVdisp supplied from the outside, and thus controls those to operate insynchronization with one another. The gate driver 12 supplies the scansignals Vscan to the liquid crystal display device 20 to sequentiallyselect one horizontal line as a display drive object. The source driver13 generates the pixel signal Vsig with the pixel signals Vpixmultiplexed and the switching control signal Vsel corresponding to thepixel signal Vsig, and supplies the generated signals to the selectionswitch section 14. The selection switch section 14 demultiplexes thepixel signals Vpix based on the pixel signal Vsig and the switchingcontrol signal Vsel, and supplies the pixel signals Vpix to therespective pixels Pix defining the one horizontal line. The drive signalgeneration section 15 generates the DC drive signal VcomDC and the ACdrive signal VcomAC. The drive electrode driver 16 sequentially appliesthe AC drive signal VcomAC to the drive electrode blocks B whileapplying the DC drive signal VcomDC to the drive electrodes COML towhich the AC drive signal VcomAC is not applied. The display device witha touch detection function 10 performs display operation whileperforming touch detection operation so that the touch detectionelectrodes TDL output the touch detection signal Vdet. The LPF section42 removes high frequency components (noise components) contained in thetouch detection signal Vdet to extract touch components for output. TheA/D conversion section 43 converts the analog signals output from theLPF section 42 into digital signals. The signal processing section 44detects presence of a touch event to the display device with a touchdetection function 10 based on the signals output from the A/Dconversion section 43. Upon detection of a touch event by the signalprocessing section 44, the coordinate extraction section 45 determinesthe touch-panel coordinates of the touch event. The detection timingcontrol section 46 controls the LPF section 42, the A/D conversionsection 43, the signal processing section 44, and the coordinateextraction section 45 to operate in synchronization with one another.

Detailed Operation

Detailed operation of the display panel with a touch detection function1 is now described.

FIG. 13 illustrates an exemplary timing waveform of the display panelwith a touch detection function 1, where (A) illustrates a waveform ofthe AC drive signal VcomAC, (B) illustrates a waveform of the DC drivesignal VcomDC, (C) illustrates waveforms of the scan signal Vscan, (D)illustrates a waveform of the pixel signal Vsig, (E) illustrateswaveforms of the switching control signal Vsel, (F) illustrateswaveforms of the pixel signal Vpix, (G) illustrates a waveform of theVcom selection signal VCOMSEL, (H) illustrates waveforms of the drivesignal Vcom, and (I) illustrates a waveform of the touch detectionsignal Vdet.

The display panel with a touch detection function 1 performs the displayoperation and the touch detection operation during each horizontalperiod (1H). In the display operation, the gate driver 12 sequentiallyapplies the scan signal Vscan to the scan signal lines GCL to performdisplay scan. In the touch detection operation, the drive electrodedriver 16 sequentially applies the AC drive signal VcomAC to the driveelectrode blocks B by one at a time to perform touch detection scan, andthe touch detection section 40 detects a touch event based on the touchdetection signal Vdet output from the touch detection electrodes TDL.These are described in detail below.

After start of one horizontal period (1H) at timing t0, the scan controlsection 51 of the drive electrode driver 16 changes the voltage of theVcom selection signal VCOMSEL from the low level to the high level attiming t1 ((G) of FIG. 13 ). As a result, in the drive electrode driver16, the switch SW1 is turned on while the switch SW2 is turned off in akth drive sub-section 53(k) relevant to the touch detection operation,so that the AC drive signal VcomAC ((A) of FIG. 13 ) generated by thedrive signal generation section 15 is applied as a drive signalVcom(B(k)) to the drive electrodes COML defining the corresponding kthdrive electrode block B(k) through the switch SW1 ((H) of FIG. 13 ). Ineach of the drive sub-sections 53 other than the kth drive sub-section53(k), the switch SW1 is turned off while the switch SW2 is turned on,so that the DC drive signal VcomDC ((B) of FIG. 13 ) generated by thedrive signal generation section 15 is applied to the drive electrodesCOML defining the corresponding drive electrode block B through theswitch SW2 ((H) of FIG. 13 ).

The drive signal generation section 15 then changes the voltage of theAC drive signal VcomAC from the low level to the high level at timing t2((A) of FIG. 13 ). In detail, in the drive signal generation section 15,the buffer 63 supplies a current through the switching circuit 66 basedon the Vcom control signal EXVCOM, so that the voltage of the AC drivesignal VcomAC is changed from the low level to the high level. Alongwith this, the drive signal Vcom (B(k)) applied to the kth driveelectrode block B(k) is also changed from the low level to the highlevel ((H) of FIG. 13 ). The drive signal Vcom (B(k)) is transmitted tothe touch detection electrodes TDL through capacitance, so that thevoltage of the touch detection signal Vdet is changed ((I) of FIG. 13 ).

The A/D conversion section 43 of the touch detection section 40 thenperforms A/D conversion of the signals output from the LPF section 42which has received the touch detection signal Vdet, at a sampling timingts ((I) of FIG. 13 ). The signal processing section 44 of the touchdetection section 40 detects a touch event based on the A/D conversionresults collected over a plurality of horizontal periods as describedbelow.

The drive signal generation section 15 then changes the voltage of theAC drive signal VcomAC from the high level to the low level at timing t3((A) of FIG. 13 ). In detail, in the drive signal generation section 15,the buffer 64 sinks the current through the switching circuit 66 basedon the Vcom control signal EXVCOM, so that the voltage of the AC drivesignal VcomAC is changed from the high level to the low level. Alongwith this, the drive signal Vcom (B(k)) applied to the kth driveelectrode block B(k) is also changed from the high level to the lowlevel ((H) of FIG. 13 ), so that the voltage of the touch detectionsignal Vdet is changed ((I) of FIG. 13 ).

Subsequently, the scan control section 51 of the drive electrode driver16 changes the voltage of the Vcom selection signal VCOMSEL from thehigh level to the low level at timing t4 ((G) of FIG. 13 ). As a result,in the drive electrode driver 16, the switch SW1 is turned off while theswitch SW2 is turned on in the drive sub-section 53(k), so that the DCdrive signal VcomDC ((B) of FIG. 13 ) generated by the drive signalgeneration section 15 is applied as the drive signal Vcom(B(k)) to thedrive electrodes COML defining the corresponding drive electrode blockB(k) through the switch SW2 ((H) of FIG. 13 ).

The gate driver 12 applies the scan signal Vscan to an nth scan signalline GCL(n) relevant to display operation at timing t5, so that thevoltage of the scan signal Vscan is changed from the low level to thehigh level ((C) of FIG. 13 ). In addition, the source driver 13 and theselection switch section 14 apply the pixel signals Vpix to the pixelsignal lines SGL ((F) of FIG. 13 ) for display of pixels Pix on onehorizontal line corresponding to the nth scan signal line GCL(n).

In detail, the gate driver 12 changes the scan signal Vscan from the lowlevel to the high level at timing t5 to select one horizontal linerelevant to the display operation. In addition, the source driver 13supplies a pixel voltage VR for a red sub-pixel SPix as a pixel signalVsig to the selection switch section 14 ((D) of FIG. 13 ), and generatesa switching control signal VselR that is high during a period ofsupplying the pixel voltage VR, and supplies the switching controlsignal VselR to the selection switch section 14 ((E) of FIG. 13 ). Theselection switch section 14 allows a switch SWR to be on in a periodwhere the switching control signal VselR is high (write period PW) toseparate the pixel voltage VR supplied from the source driver 13 fromthe pixel signal Vsig, and supplies the pixel voltage VR as a pixelsignal VpixR to the red sub-pixels SPix on one horizontal line throughthe pixel signal line SGL ((F) of FIG. 13 ). It is to be noted thatafter the switch SWR is turned off, the pixel signal line SGL is floatedand thus the voltage of the pixel signal line SGL is maintained ((F) ofFIG. 13 ). Similarly, the source driver 13 supplies a pixel voltage VGfor a green sub-pixel SPix together with a corresponding switchingcontrol signal VselG to the selection switch section 14 ((D) and (E) ofFIG. 13 ). The selection switch section 14 demultiplexes the pixelvoltage VG from the pixel signal Vsig based on the switching controlsignal VselG, and supplies the pixel voltage VG as a pixel signal VpixGto the green sub-pixels SPix on one horizontal line through the pixelsignal line SGL ((F) of FIG. 13 ). Similarly, the source driver 13 thensupplies a pixel voltage VB for a blue sub-pixel SPix together with acorresponding switching control signal VselB to the selection switchsection 14 ((D) and (E) of FIG. 13 ). The selection switch section 14demultiplexes the pixel voltage VB from the pixel signal Vsig based onthe switching control signal VselB, and supplies the pixel voltage VB asa pixel signal VpixB to the blue sub-pixels SPix on one horizontal linethrough the pixel signal line SGL ((F) of FIG. 13 ).

Next, the gate driver 12 changes the scan signal Vscan(n) of the scansignal line GCL (n) in the nth row from the high level to the low levelat timing t6 ((C) of FIG. 13 ). As a result, the sub-pixels SPix on theone horizontal line relevant to display operation are electricallyseparated from the pixel signal lines SGL.

Then, one horizontal period is finished and a subsequent horizontalperiod is started at timing t10.

After that, the above operation is repeated, thereby the display panelwith a touch detection function 1 performs display operation over theentire display surface through line-sequential scan, and performs touchdetection operation over the entire touch-detection surface throughscanning the drive electrode blocks B by one at a time.

FIG. 14 illustrates an exemplary operation of the touch detection scan,where (A) illustrates a waveform of the AC drive signal VcomAC, (B)illustrates a waveform of the DC drive signal VcomDC, (C) illustrates awaveform of the Vcom selection signal VCOMSEL, (D) illustrates waveformsof the scan signal St, (E) illustrates waveforms of the drive signalVcom, and (F) illustrates a waveform of the touch detection signal Vdet.

As shown in FIG. 14 , the drive electrode driver 16 sequentially appliesthe AC drive signal VcomAC to the corresponding drive electrode block B((E) of FIG. 14 ) based on the scan signal St ((D) of FIG. 14 )generated by the touch detection scan section 52 to perform touchdetection scan. During this, the drive electrode driver 16 applies theAC drive signal VcomAC to each of the drive electrode blocks B over aplurality of predetermined horizontal periods ((E) of FIG. 14 ). Thetouch detection section 40 samples the touch detection signal Vdet basedon the AC drive signal VcomAC during each one horizontal period. Aftersuch sampling is finished in the last horizontal period among theplurality of predetermined horizontal periods, the signal processingsection 44 detects presence of a touch event in a region correspondingto the relevant drive electrode block B based on the plurality ofsampling results. In this way, touch detection is performed based on theplurality of sampling results. As a result, the sampling results arestatistically analyzed. This suppresses a reduction in an S/N ratio dueto variations in the sampling results, leading to an improvement inaccuracy of touch detection.

Comparative Example

The functions of the display panel with a touch detection function 1according to the embodiment are now described in comparison with adisplay panel with a touch detection function according to a comparativeexample. In the comparative example, a drive signal generation sectiongenerates high and low, two kinds of DC drive signals, and a driveelectrode driver selects one of the two DC drive signals and applies theselected DC drive signal to drive electrodes COML. Other configurationsare the same as in the embodiment (FIG. 4 and others).

FIG. 15 illustrates an exemplary configuration of a drive signalgeneration section 15R according to the comparative example. The drivesignal generation section 15R generates two kinds of DC drive signalsVcomH and VcomDC. The DC drive signal VcomH is generated by ahigh-level-voltage generation sub-section 61 and output through a buffer63. The DC drive signal VcomDC is generated by a low-level-voltagegeneration sub-section 62 and output through a buffer 65.

FIG. 16 illustrates an exemplary configuration of a drive electrodedriver 16R according to the comparative example. The drive electrodedriver 16R includes a scan control section 51R. The scan control section51R supplies a Vcom selection signal VCOMSELR to a drive section 530.The Vcom selection signal VCOMSELR indicates appropriate one of the twokinds of DC drive signals VcomH and VcomDC to be supplied to the driveelectrodes COML.

The drive electrode driver 16R has switches SW1 each having one end towhich the DC drive signal VcomH is supplied, as shown in FIG. 16 .According to such a configuration, if a scan signal St is high, thedrive sub-section 53 outputs the DC drive signal VcomH as a drive signalVcom while the Vcom selection signal VCOMSELR is high, and outputs theDC drive signal VcomDC as the drive signal Vcom while the Vcom selectionsignal VCOMSELR is low.

FIG. 17 illustrates an exemplary timing waveform of the display panelwith a touch detection function according to the comparative example,where (A) illustrates a waveform of the DC drive signal VcomH, (B)illustrates a waveform of the DC drive signal VcomDC, (C) illustrateswaveforms of a scan signal Vscan, (D) illustrates a waveform of a pixelsignal Vsig, (E) illustrates waveforms of a switching control signalVsel, (F) illustrates waveforms of a pixel signal Vpix, (G) illustratesa waveform of the Vcom selection signal VCOMSELR, (H) illustrateswaveforms of a drive signal Vcom, and (I) illustrates a waveform of atouch detection signal Vdet.

The scan control section 51R of the drive electrode driver 16R changesthe voltage of the Vcom selection signal VCOMSELR from the low level tothe high level at timing t11 ((G) of FIG. 17 ). As a result, in thedrive electrode driver 16, the switch SW1 is turned on while a switchSW2 is turned off in a kth drive sub-section 53(k) relevant to the touchdetection operation, so that the DC drive signal VcomH ((A) of FIG. 17 )generated by the drive signal generation section 15R is applied as adrive signal Vcom(B(k)) to the drive electrodes COML, defining thecorresponding kth drive electrode block B(k) through the switch SW1 ((H)of FIG. 17 ). In detail, the buffer 63 of the drive signal generationsection 15R supplies a current to the drive electrodes COML, so that thedrive signal Vcom(B(k)) is changed from the low level to the high level.In each of the drive sub-sections 53 other than the drive sub-section53(k), the switch SW1 is turned off while the switch SW2 is turned on,so that the DC drive signal VcomDC ((B) of FIG. 17 ) generated by thedrive signal generation section 15R is applied to the drive electrodesCOML defining the corresponding drive electrode block B through theswitch SW2 ((H) of FIG. 17 ). An A/D conversion section 43 of a touchdetection section 40 then performs A/D conversion of the signals outputfrom an LPF section 42 which has received the touch detection signalVdet, at a sampling timing ts ((I) of FIG. 17 ).

The scan control section 51R of the drive electrode driver 16R changesthe voltage of the Vcom selection signal VCOMSELR from the high level tothe low level at timing t12 ((G) of FIG. 17 ). As a result, in the driveelectrode driver 16R, the switch SW1 is turned off while the switch SW2is turned on in the kth drive sub-section 53(k), so that the DC drivesignal VcomDC ((B) of FIG. 17 ) generated by the drive signal generationsection 15R is applied as the drive signal Vcom(B(k)) to the driveelectrodes COML, defining the corresponding drive electrode block B(k)through the switch SW2 ((H) of FIG. 17 ). In detail, the buffer 65 ofthe drive signal generation section 15R sinks the current from the driveelectrodes COML, so that the voltage of the drive signal Vcom(B(k)) ischanged from the high level to the low level.

At that time, the buffer 65 of the drive signal generation section 15Rdrives all the drive electrodes COML through the switches SW2 of thedrive section 530 of the drive electrode driver 16R. Thus, the buffer 65may not sufficiently drive the drive electrodes COML due to a largeload. In such a case, at and after timing t2, electric charge, which hasbeen accumulated in the drive electrodes COML of the drive electrodeblock B(k) during application of the DC drive signal VcomH, moves toother drive electrode blocks B through the switch SW2 of the drivesub-section 53(k), resulting in rising of the voltage of the drivesignal Vcom (Vcom(B(k-1), Vcom(B(k), Vcom(B(k+1) and others) applied tothe drive electrode blocks B (wavy portions WR). The buffer 65 sinkssuch electric charge, so that the voltage of the drive signal Vcomgradually converges to the voltage level of the DC drive signal VcomDC.If such converging time is long, nearly the write period PW, the pixelsignal Vpix is insufficiently written into the pixels during therelevant write period PW, leading to a possibility of a reduction inimage quality.

Contrarily, in the display panel with a touch detection functionaccording to the embodiment, as shown in (H) of FIG. 13 , the AC drivesignal VcomAC is changed from the high level to the low level at timingt3, and then the switch SW1 is turned off while the switch SW2 is turnedon at timing t4 in the drive sub-section 53(k), so that the drive signalsupplied to the drive electrodes COML is switched from the AC drivesignal VcomAC to the DC drive signal VcomDC.

As a result, in the drive signal generation section 15, the buffer 64,which is different from the buffer 65 generating the DC drive signalVcomDC, sinks the current at the timing when the AC drive signal VcomACis changed from the high level to the low level at timing t3, andtherefore the DC drive signal VcomDC is less affected by the AC drivesignal VcomAC. Specifically, noise in the DC drive signal VcomDC, whichis supplied to the horizontal line to which display operation isperformed, is suppressed, thereby suppressing a reduction in imagequality.

In addition, since the electric potential of the drive electrode blockB(k) (the low-level voltage of the AC drive signal VcomAC) issubstantially equal to the electric potential of other drive electrodeblocks B(k) (the DC voltage of the DC drive signal VcomDC) immediatelybefore the timing t4, substantially no electric charge moves after theswitch SW2 is turned on at the timing t4. This reduces rising of thevoltage of the drive signal Vcom (B(k)) as shown in the wavy portions WRin the comparative example, thereby suppressing a reduction in imagequality.

Effect

As described before, in the embodiment, the AC drive signal and the DCdrive signal are selectively applied to the drive electrodes to bedriven, and the DC drive signal is switched from the AC drive signalafter the AC drive signal is changed from the high level to the lowlevel, thereby suppressing a reduction in image quality.

In addition, in the embodiment, the buffer for supplying the low levelof the AC drive signal and the buffer for supplying the DC drive signalare separately provided, thereby suppressing a reduction in imagequality.

Modification 1-1

While the drive signal generation section 15 is configured as shown inFIG. 11 in the first embodiment, this is not limitative. For example, abuffer 64A for generating the low level of the AC drive signal mayreceive the DC drive signal VcomDC, as shown in FIG. 18 . Thelow-level-voltage generation sub-section 62 and the buffer 65 correspondto a specific example of “second voltage generation section” of thedisclosure. The buffer 64A corresponds to a specific example of “buffercircuit” of the disclosure. In this case, the DC drive signal VcomDC isalso less affected by the noise due to the AC drive signal VcomAC,thereby suppressing a reduction in image quality.

Modification 1-2

While the drive electrode driver 16 drives the drive electrode blocks B,each including the predetermined number of drive electrodes COML, by oneat a time in the first embodiment, this is not limitative. Instead, thedrive electrode driver 16 may directly drive the drive electrodes COMLby one at a time, for example, as shown in FIG. 19 . In such a case, adrive section 530B includes the same number of drive sub-sections 53 asthe total number of the drive electrodes COML, and a touch detectionscan section 52B supplies the scan signals St to the drive section 530B.

Modification 1-3

While the drive electrodes COML are scanned to be driven by onedrive-electrode-block B, which includes the predetermined number ofdrive electrodes COML, at a time, this is not limitative. Instead, forexample, a predetermined number of drive electrodes COML may besimultaneously driven while the drive electrodes COML to be driven areshifted one by one to scan the drive electrodes COML. This is describedin detail below.

FIG. 20 schematically illustrates an exemplary operation of a driveelectrode driver 16C according to the modification. The drive electrodedriver 16C simultaneously applies the AC drive signal VcomAC to apredetermined number of drive electrodes COML. In detail, the driveelectrode driver 16C simultaneously applies the AC drive signal VcomACto the predetermined number (here, five) of drive electrodes COML(drive-signal-applied electrodes LAC). Then, the drive electrode driver16C shifts the drive electrodes COML, to which the AC drive signalVcomAC is applied, one by one to perform touch detection scan. Suchtouch detection scan is achieved by, for example, using the driveelectrode driver 16B shown in FIG. 19 , where a shift register in thetouch detection scan section 52B transmits a wide pulse. While the ACdrive signal VcomAC is simultaneously applied to the five driveelectrodes COML herein, this is not limitative. Instead, the AC drivesignal VcomAC may be simultaneously applied to not more than four driveelectrodes COML or not less than six drive electrodes COML. While thedrive electrodes COML, to which the AC drive signal VcomAC is applied,are shifted one by one herein, this is not limitative. Instead, thedrive electrodes COML may be shifted by two or more at a time.

Modification 1-4

While the voltage of the AC drive signal VcomAC is changed from the lowlevel to the high level at timing t2 after the voltage of the Vcomselection signal VCOMSEL is changed from the low level to the high levelat timing t1 as shown in FIG. 13 in the first embodiment, this is notlimitative. For example, the voltage of the Vcom selection signalVCOMSEL may be changed from the low level to the high level at timingt22 after the voltage of the AC drive signal VcomAC is changed from thelow level to the high level at timing t21, as shown in FIG. 21 .

3. Second Embodiment

A display panel with a touch detection function 7 according to a secondembodiment is now described. The second embodiment is different from thefirst embodiment in a selection process of the drive signal in the casewhere one of the DC drive signal VcomDC and the AC drive signal VcomACis selected to be supplied to the drive electrodes COML. It is to benoted that substantially the same components as those of the displaypanel with a touch detection function 1 according to the firstembodiment are designated by the same numerals, and description of themis appropriately omitted.

FIG. 22 illustrates an exemplary configuration of a drive electrodedriver 18 of the display panel with a touch detection function 7. Thedrive electrode driver 18 includes a scan control section 71 and a drivesection 730.

The scan control section 71 supplies a control signal to a touchdetection scan section 52 based on a control signal supplied from acontrol section 11.

The drive section 730 applies a drive signal Vcom (a DC drive signalVcomDC or an AC drive signal VcomAC) to the drive electrodes COML basedon a scan signal St supplied from the touch detection scan section 52.Each drive sub-section 73 includes an inverter 55, buffers 56 and 57,and switches SW1 and SW2. Specifically, the drive sub-section 73 doesnot include an AND gate 54 unlike the drive sub-section 53 in the firstembodiment. According to such a configuration, the drive sub-section 73outputs the AC drive signal VcomAC as the drive signal Vcom if the scansignal St is high, and outputs the DC drive signal VcomDC as the drivesignal Vcom if the scan signal St is low.

FIG. 23 illustrates an exemplary timing waveform of the display panelwith a touch detection function 7, where (A) illustrates a waveform ofthe AC drive signal VcomAC, (B) illustrates a waveform of the DC drivesignal VcomDC, (C) illustrates waveforms of the scan signal Vscan, (D)illustrates a waveform of a pixel signal Vsig, (E) illustrates waveformsof a switching control signal Vsel, (F) illustrates waveforms of a pixelsignal Vpix, (G) illustrates waveforms of the drive signal Vcom, and (H)illustrates a waveform of a touch detection signal Vdet.

Upon start of one horizontal period (1H) at timing t0, the driveelectrode driver 18 supplies the AC drive signal VcomAC to the driveelectrodes COML relevant to touch detection ((G) of FIG. 23 ). Indetail, in the drive electrode driver 18, the switch SW1 is turned onwhile the switch SW2 is turned off in a kth drive sub-section 73(k)relevant to the touch detection operation, so that the AC drive signalVcomAC ((A) of FIG. 23 ) generated by the drive signal generationsection 15 is applied as a drive signal Vcom(B(k)) to the driveelectrodes COML, defining the corresponding kth drive electrode blockB(k) through the switch SW1 ((G) of FIG. 23 ).

The drive signal generation section 15 then changes the voltage of theAC drive signal VcomAC from the low level to the high level at timing t2((A) of FIG. 23 ). Along with this, the drive signal Vcom (B(k)) appliedto the kth drive electrode block B(k) is changed from the low level tothe high level ((G) of FIG. 23 ). The drive signal Vcom (B(k)) istransmitted to touch detection electrodes TDL through capacitance, sothat the voltage of the touch detection signal Vdet is changed ((H) ofFIG. 23 ). An A/D conversion section 43 of a touch detection section 40then performs A/D conversion of the signals output from an LPF section42 which has received the touch detection signal Vdet, at a samplingtiming ts ((H) of FIG. 23 ). The drive signal generation section 15 thenchanges the voltage of the AC drive signal VcomAC from the high level tothe low level at timing t3 ((A) of FIG. 23 ).

At and after timing t5, the display panel with a touch detectionfunction 7 performs display operation as in the display panel with atouch detection function 1 according to the first embodiment. In thedisplay panel with a touch detection function 7, the drive electrodedriver 18 still applies the AC drive signal VcomAC as the drive signalVcom(B(k)) to the drive electrodes COML relevant to the touch detectionduring a period of the display operation ((G) of FIG. 23 ).

FIG. 24 illustrates an exemplary operation of the touch detection scanof the display panel with a touch detection function 7, where (A)illustrates a waveform of the AC drive signal VcomAC, (B) illustrates awaveform of the DC drive signal VcomDC, (C) illustrates waveforms of thescan signal St, (D) illustrates waveforms of the drive signal Vcom, and(E) illustrates a waveform of the touch detection signal Vdet.

As shown in FIG. 24 , the drive electrode driver 18 sequentially appliesthe AC drive signal VcomAC to the relevant drive electrode block B basedon the scan signal St ((C) of FIG. 24 ) generated by the touch detectionscan section 52 ((D) of FIG. 24 ) to perform touch detection scan. Inthis operation, the drive electrode driver 18 continuously supplies theAC drive signal VcomAC to the corresponding kth drive electrode blockB(k) during a period where the kth scan signal St(k) is high, forexample. Specifically, in the first embodiment, the AC drive signalVcomAC is applied only while the Vcom selection signal VCOMSEL is highin the period where the kth scan signal St(k) is high, as shown in (E)of FIG. 14 . Contrarily, in the second embodiment, the AC drive signalVcomAC is continuously applied in the period where the kth scan signalSt(k) is high, as shown in (D) of FIG. 24 .

The AC drive signal VcomAC or the DC drive signal VcomDC is applied tothe drive electrode COML along one horizontal line relevant to thedisplay operation. In detail, in the case where the drive electrode COMLalong one horizontal line relevant to the display operation is notincluded in the drive detection block B relevant to touch detectionoperation, the DC drive signal VcomDC is applied to the drive electrodeCOML. Contrarily, the drive electrode COML along one horizontal linerelevant to the display operation is included in the drive detectionblock B relevant to the touch detection operation at the timing W1 inFIG. 10 . In such a case, the AC drive signal VcomAC is applied to thedrive electrode COML. The DC voltage of the DC drive signal VcomDC andthe low-level voltage of the AC drive signal VcomAC are generated by thelow-level-voltage generation sub-section 62 of the drive signalgeneration section 15 as shown in FIG. 11 and thus have substantiallythe same voltage level. In this way, since the voltage of the driveelectrode COML along one horizontal line relevant to the displayoperation is substantially the same between the case where the onehorizontal line corresponds to the drive detection block B relevant tothe touch detection operation and another case, substantially the samepixel signal is written during the write period PW, thereby suppressinga reduction in image quality.

It is to be noted that in the case where the DC voltage of the DC drivesignal VcomDC is slightly different from the low-level voltage of the ACdrive signal VcomAC due to a difference in performance between thebuffers 64 and 65 (FIG. 11 ), the voltage is differently written into apixel between the case where the DC drive signal VcomDC is supplied tothe drive electrode COML along one horizontal line relevant to thedisplay operation and the case where the AC drive signal VcomAC issupplied thereto, leading to a possibility of degradation in imagequality. In such a case, the AC drive signal VcomAC is desirably appliedto the drive electrode COML during periods other than the write periodPW as in the display panel with a touch detection function 1 of thefirst embodiment.

As described above, in the second embodiment, the drive signal suppliedto the drive electrode is selected only based on the scan signal St,which simplifies the configurations of the scan control section and thedrive section. Other effects are the same as in the first embodiment.

Modification 2

In the second embodiment, the drive signal generation section 15 may beconfigured as shown in FIG. 18 , for example, as in the modification 1-1of the first embodiment. In addition, the drive electrode driver 18 maydirectly drive the drive electrodes COML by one at a time as in themodification 1-2 of the first embodiment. In addition, touch detectionscan may be performed as shown in FIG. 20 as in the modification 1-3 ofthe first embodiment.

3. Application Examples

Next, application examples of each display panel with a touch detectionfunction in the above-described embodiments and modifications are nowdescribed with reference to FIGS. 25 to 29G. The display panel with atouch detection function described in the embodiments and others isapplicable to electronic units in various fields, including a televisionapparatus, a digital camera, a notebook personal computer, a mobileterminal device such as a mobile phone, and a video camera. In otherwords, the display panel with a touch detection function in theembodiments and others is applicable to electronic units in variousfields for displaying externally-input or internally-generated videosignals as still or video images.

Application Example 1

FIG. 25 shows appearance of a television apparatus applied with thedisplay panel with a touch detection function according to theembodiments and others. The television apparatus has, for example, animage display screen section 510 including a front panel 511 and afilter glass 512. The image display screen section 510 is configured ofthe display panel with a touch detection function according to theembodiments and others.

Application Example 2

FIGS. 26A and 26B show appearance of a digital camera applied with thedisplay panel with a touch detection function according to theembodiments and others. The digital camera has, for example, a lightemitting section for flash 521, a display section 522, a menu switch523, and a shutter button 524. The display section 522 is configured ofthe display panel with a touch detection function according to theembodiments and others.

Application Example 3

FIG. 27 shows appearance of a notebook personal computer applied withthe display panel with a touch detection function according to theembodiments and others. The notebook personal computer has, for example,a main body 531, a keyboard 532 for input operation of letters and thelike, and a display section 533 for displaying images. The displaysection 533 is configured of the display panel with a touch detectionfunction according to the embodiments and others.

Application Example 4

FIG. 28 shows appearance of a video camera applied with the displaypanel with a touch detection function according to the embodiments andothers. The video camera has, for example, a main body section 541, anobject-shooting lens 542 provided on a front side face of the main bodysection 541, a start/stop switch 543 for shooting, and a display section544. The display section 544 is configured of the display panel with atouch detection function according to the embodiments and others.

Application Example 5

FIGS. 29A to 29G show appearance of a mobile phone applied with thedisplay panel with a touch detection function according to theembodiments and others. For example, the mobile phone is configured ofan upper housing 710 and a lower housing 720 connected to each other bya hinge section 730, and has a display 740, a sub display 750, a picturelight 760, and a camera 770. The display 740 or the sub display 750 isconfigured of the display panel with a touch detection functionaccording to the embodiments and others.

While the present technology has been described with the severalembodiments, the modifications, and the application examples toelectronic units hereinbefore, the technology is not limited to theembodiments and others, and various modifications or alterations may bemade.

For example, while the drive electrodes COML are provided on the TFTsubstrate 21 and the pixel electrodes 22 are provided on the driveelectrodes COML with the insulating film 23 therebetween as shown inFIG. 6 in the embodiments and others, this is not limitative. Instead,for example, the pixel electrodes 22 may be provided on the TFTsubstrate 21, and the drive electrodes COML may be provided on the pixelelectrodes 22 with the insulating film 23 therebetween.

For example, while the touch detection device is integrated with theliquid crystal display device including liquid crystal of a transverseelectric mode such as a FFS mode and an IPS mode in the embodiments andothers, the touch detection device may be integrated with a liquidcrystal display device including liquid crystal of various modes such asa twisted nematic (TN) mode, a vertical alignment (VA) mode, and anelectrically controlled birefringence (ECB) mode instead. In the casewhere such liquid crystal is used, the display device with a touchdetection function is configured as shown in FIG. 30 . FIG. 30illustrates an exemplary sectional structure of a major part of adisplay device with a touch detection function 10D, showing aconfiguration where a liquid crystal layer 6B is sandwiched between apixel substrate 2B and a counter substrate 3B. Since names and functionsof other sections are similar to those shown in the case of FIG. 6 ,description of them is omitted. This example is different from the caseof FIG. 6 in that the drive electrodes COML used for both display andtouch detection are provided on the counter substrate 3B.

In addition, while, for example, a so-called in-cell type displaydevice, where a liquid crystal display device is integrated with acapacitance-type touch detection device, is used in the above-describedembodiments and others, this is not limitative. Instead, for example, aso-called on-cell type display device, where the capacitance-type touchdetection device is mounted on the surface of the liquid crystal displaydevice, may be used. In the on-cell type display device, for example, inthe case where noise in touch detection drive is transmitted from thetouch detection device to the liquid crystal display device, the noiseis reduced through the driving as in the embodiments, leading tosuppression of a reduction in image quality of the liquid crystaldisplay device.

In addition, for example, while the liquid crystal elements are used forthe display elements in the above-described embodiments and others, thisis not limitative. Instead, electro luminescence (EL) elements may beused, for example.

It is possible to achieve at least the following configurations from theabove-described exemplary embodiments and the modifications of thedisclosure.

(1) A display panel with a touch detection function including:

-   one or more display elements;-   one or more drive electrodes;-   one or more touch detection electrodes; and-   a drive section selectively applying a DC drive signal or an AC    drive signal to the drive electrodes.

The display panel according to (1),

-   wherein the display elements perform write operation for display    during a write period,-   the AC drive signal has a pulse waveform that transits from a first    voltage to a second voltage corresponding to a DC voltage level of    the DC drive signal at a transition timing in a period other than    the write period,-   the drive section applies the AC drive signal to the drive    electrodes in an enable period including the transition timing, and    applies the DC drive signal to the drive electrodes in a period    other than the enable period to perform touch detection drive.

The display panel according to (2),

-   wherein the AC drive signal has a pulse waveform that includes the    first voltage in a pulse period different from the write period, and    includes the second voltage in a period other than the pulse period,    and-   the transition timing corresponds to end timing of the pulse period.

The display panel according to (3), wherein the enable period is in aperiod other than the write period.

The display panel according to (3) or (4), wherein the enable periodincludes the pulse period.

The display panel according to (3),

-   wherein the plurality of display elements are arranged in a matrix    and line-sequentially scanned for display operation, and-   the enable period corresponds to one horizontal period or    consecutive, multiple horizontal periods.

The display panel according to any one of (1) to (6), further including

-   a drive signal generation section generating the DC drive signal and    the AC drive signal,-   wherein the drive signal generation section includes-   a first-voltage generation sub-section generating the first voltage,-   a second-voltage generation sub-section generating a voltage    corresponding to a DC voltage level of the DC drive signal,-   a buffer circuit generating the second voltage based on the voltage    output from the second voltage generation sub-section, and-   a switching circuit generating the AC drive signal through switching    the first voltage and the second voltage from each other.

The display panel according to any one of (2) to (7), further including

-   a touch detection section,-   wherein the drive electrodes are formed to extend in a predetermined    direction,-   the touch detection electrodes are formed to extend in a direction    crossing the extending direction of the drive electrodes in a layer    different from a layer of the drive electrodes, and-   the drive section sequentially selects one or more drive electrodes    among the drive electrodes as a drive object electrode, and drives    the drive object electrode for touch detection while applying the DC    drive signal to drive electrodes other than the drive object    electrode, and-   the touch detection section detects a touch event based on signals    output from the touch detection electrodes.

The display panel according to any one of (1) to (8),

-   wherein the display element includes-   a liquid crystal layer, and-   a pixel electrode provided between the liquid crystal layer and the    drive electrodes, or disposed facing the liquid crystal layer with    the drive electrodes therebetween.

The display panel according to any one of (1) to (8),

-   wherein the display element includes-   a liquid crystal layer, and-   a pixel electrode disposed facing the drive electrodes with the    liquid crystal layer therebetween.

A method of driving a display panel with a touch detection function,including:

-   driving one or more display elements for display; and-   selectively applying a DC drive signal or an AC drive signal to one    or more drive electrodes.

A drive circuit including:

-   a display drive section driving one or more display elements; and-   a touch detection drive section selectively applying a DC drive    signal or an AC drive signal to one or more drive electrodes.

An electronic unit including:

-   a display panel with a touch detection function; and-   a control section controlling operation using the display panel with    a touch detection function,-   wherein the display panel with a touch detection function includes-   one or more display elements,-   one or more drive electrodes,-   one or more touch detection electrodes, and-   a drive section selectively applying a DC drive signal or an AC    drive signal to the drive electrodes.

The present disclosure contains subject matter related to that disclosedin Japanese Priority Patent Application JP 2011-89429 filed in the JapanPatent Office on Apr. 13, 2011 and Japanese Priority Patent ApplicationJP 2011-242797 filed in the Japan Patent Office on Nov. 4, 2011, theentire content of which is hereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A fringe field switching (FFS) display panelcomprising: a plurality of pixel electrodes; a plurality of commonelectrodes; and a driving circuit configured to output a first drivesignal or a second drive signal different from the first drive signalfor driving at least one of the common electrodes, wherein the firstdrive signal is output to perform a display operation on the displaypanel during a first period, and the second drive signal is output toperform a touch detection in a second period other than the firstperiod.
 2. The FFS display panel according to claim 1, wherein the firstdrive signal is a DC signal, the second drive signal is an AC signal,the first period is a display period, and the second period is a touchdetection period.
 3. The FFS display panel according to claim 2, whereinthe driving circuit drives at least one common electrode in the touchdetection period.
 4. The FFS display panel according to claim 3, whereinthe driving circuit drives the common electrodes in the touch detectionperiod.
 5. The FFS display panel according to claim 1, furthercomprising: a touch detection circuit, wherein the driving circuit isconfigured to: sequentially select at least one of the common electrodeseach extending in a predetermined direction, as a drive objectelectrode; and drive the drive object electrode for touch detectionwhile applying the first drive signal to at least one of the commonelectrodes other than the drive object electrode, and the touchdetection circuit comprises a touch detection section that detects atouch event based on signals output from the drive object electrodes. 6.The FFS display panel according to claim 1, further comprising a switchelement to apply: the first drive signal to at least one of the commonelectrodes in the first period; and the second drive signal to at leastone of the common electrodes in the second period.
 7. The FFS displaypanel according to claim 1, further comprising an AC-drive-signal wireand a DC-drive-signal wire, wherein the driving circuit is configured tooutput: the second drive signal supplied from the AC-drive-signal wire;and the first drive signal supplied from the DC-drive-signal wire. 8.The FFS display panel according to claim 1, further comprising a firstDC-drive-signal wire and a second DC-drive-signal wire, and the drivingcircuit is configured to output: the second drive signal that is asignal alternately supplied from the first DC-drive-signal wire and thesecond DC-drive-signal wire; and the first drive signal that is either afirst DC drive signal from the first DC-drive-signal wire or a second DCdrive signal from the second DC-drive-signal wire.
 9. The FFS displaypanel according to claim 8, wherein the driving circuit is configured tooutput the second DC drive signal supplied from the secondDC-drive-signal wire, the second DC drive signal being lower than thefirst DC drive signal supplied from the first DC-drive-signal wire. 10.The FFS display panel according to claim 7, wherein the second drivesignal supplied to the AC-drive-signal wire is a signal generated byallowing a buffer circuit to alternately switch a first power source tooutput a first DC voltage and a second power source to output a secondDC voltage that is lower than the first DC voltage.
 11. The FFS displaypanel according to claim 8, wherein a first DC drive voltage supplied tothe first DC-drive-signal wire is supplied from the first power source,a second DC drive voltage supplied to the second DC-drive-signal wire issupplied from the second power source, and the second DC voltage islower than the first DC voltage.
 12. The FFS display panel according toclaim 1, further comprising: a plurality of pixel electrodes and aplurality of common electrodes, wherein the driving circuit is includedin an IC chip.
 13. The FFS display panel according to claim 1, furthercomprising a switch element to apply: the first drive signal to at leastone of the common electrodes in the first period; and the second drivesignal to at least one of the common electrodes in the second period.14. The FFS display panel according to claim 1 further comprising anAC-drive-signal wire and a DC-drive-signal wire, wherein the seconddrive signal supplied from the AC-drive-signal wire; and the first drivesignal supplied from the DC-drive-signal wire.
 15. The FFS display panelaccording to claim 12, further comprising a first DC-drive-signal wireand a second DC-drive-signal wire, and the IC chip is configured tooutput: the second drive signal that is a signal alternately suppliedfrom the first DC-drive-signal wire and the second DC-drive-signal wire;and the first drive signal that is either a first DC drive signal fromthe first DC-drive-signal wire or a second DC drive signal from thesecond DC-drive-signal wire.
 16. The FFS display panel according toclaim 15, wherein the IC chip is configured to output the second DCdrive signal supplied from the second DC-drive-signal wire, the secondDC drive signal being lower than the first DC drive signal supplied fromthe first DC-drive-signal wire.
 17. The FFS display panel according toclaim 14, wherein the second drive signal supplied to theAC-drive-signal wire is a signal generated by allowing a buffer circuitto alternately switch a first power source to output a first DC voltageand a second power source to output a second DC voltage that is lowerthan the first DC voltage.